Control system for airplanes



Junell, 1946. E F,ZA P 2,402,001

CONTROL SYSTEM FOR AIRPLANES FiledMaroh l5, 1941 5 Sheets-Sheet 1 HARP/J, K/cbg Fo a HA RAe/5 Gig MM .PQR 771 FIRM June 11,1946. E, F ZAP 2,402,001

' CONTROL SYSTEM FOR AIRPLANES I Filed March 15, 1941 5 Sheeizs-Smaerl 2 AIL ERON ELEVA TIO/V 4/L ERON ELEVT/ON l 35 4 La@ For THE FIRM A rro @we Ks June 11, 1946. E. ,ZA

CONTROL SYSTEM vFOR AIRPLANES 5 Sheets-Shree?l 5 Filed March l5, 1941 June 11, 1946. E F ZAP CONTROL SYSTEM FOR A'IRPLANES Filed March 15, 1941 5 SheetS-She'et 4 POG/T/ON OF CONTROL WICK //v A5/v To@ EDWARD FZAP u R M H. R m. w H C K JI Y @m H June 11', 1946.

E. F. ZAP

CONTROL SYSTEM FOR AIRPLANES Filed March 15, 1941 Patented June 11, 1946 UNITED STATES PATENT OFFICE CONTROL SYSTEM FOR AIRPLANES Edward F. Zap, Los Angeles, Calif.

Application March 1 5, 1941, Serial No. 383,570

3 Claims. l

My invention relates to control system for pairs of aerodynamic members, such as pairs of ailerons or pairs of flaps, in which systems the two aerodynamic members have opposite ightcontrol effects and are both governed by a common means such as the usual control stick,

While the invention is broadly applicable to various control problems in aircraft operation, it is being initially applied to the control of a pair of ailerons of a particular type. The description herein of such an embodiment of the invention will be adequate guidance for applying the underlying principles of the invention to other flight-control systems.

The general object of the invention is to provide a positive, reliable, and sensitive control for a cooperating pair of aerodynamic members or ailerons.

In the rolling control of an aircraft by a pair of ailerons of the type herein disclosed, it is required that each aileron dwell or remain stationary at some stage while the other aileron is being moved by the common control stick. One object of the invention is to provide operative connections between the control stick and the two ailerons that will afford the requisite dwells in the operation of each aileron; and a further object is to incorporate in such operative connections suitable means to substantially lock the ailerons substantially in their dwell positions. A still further object is to make such operative connections reversible in the sense of transmitting to the control stick at least a portion of the aerodynamic forces encountered by the ailerons, thereby to make the aerodynamic forces perceptible to the pilot.

One problem encountered in designing a control system involving the present type as well as other types of ailerons is to achieve sensitivity of control immediately adjacent the neutral Dosition of the control stick. In other words, it is required that the aircraft be denitely and instantly responsive to even minor lateral movements of the control stick from its normal neutral position. To have a central dead Zone in the range of stick movement or even an appreciable zone of relatively low response is intolerable, especially in a modern military airplane. One object of the present invention is to achieve such sensitivity of control.

It is a further object of the invention to provide a relatively rapid rise of night-control forces as the control stick initially departs in either lateral direction from its neutral position. It is proposed that the magnitude of the engendered vide an aileron-control arrangement that is not critical in adjustment and in which looseness of connections cannot develop a non-responsive zone in the range of control stick positions.

Other objects of the invention, especially specic objects relating to the mechanics of the control system and objects relating to novel forms of ailerons will be apparent in the following detailed description, taken With the accompanying drawings.

In the drawings which are to be considered as illustrative only:

Fig. 1 is a plan view of the control system as extended through one wing of an airplane, the outline of the wing and fuselage of the aircraft being shown in dash-dot lines;

Fig. 2 is an enlarged transverse section of a wing incorporating my control system, the section being taken as indicated by the broken line 2--2 of Fig. 1;

Fig. 3 is a greatly enlarged fragmentary section taken along the arcuate line 3 3 of Fig. 2;

Fig. 4 is a transverse section taken as indicate by the line 4-4 of Fig. 3;

Fig. 5 is an enlarged front elevation of a portion of the control system as viewed along the line 5 5 of Fig. 1, the control mechanism being in normal neutral disposition;

Fig. 6 is a similar View of the control mechanism at one of its operating positions,

Fig. 7 is a diagram of operation of one adjustment of the control system;

Fig. 8 is a diagram of operation of a second adjustment of the control system;

Fig. 9 is a fragmentary plan view showing a modification of the aileron construction;

Fig. 10 is a plan View on an enlarged scale of certain cranks that may be substituted in the arrangement shown in Fig. 1 in one practice of my invention;

Fig. 11 is a chart indicating the operations of the various aileron panels when the cranks of Fig. 10 are employed; f

Fig. 12 is a View similar to Fig. 2 indicating the construction of a modified aileron arrangement;

Fig. 13 is an enlarged fragmentary cross section taken as indicated by the line |3-I3 of Fig. 12;

Fig. 14 is a View similar to Fig. 2 showing another form of aileron panel that may be employed;

Fig. 15 is a fragmentary view taken as indicated by the arrow I in Fig. 14;

Fig. 16 is an enlarged fragmentary section taken as indicated by the line lS-IB of-Fig. 15;

Fig. 17 is a diagrammatic view in section sho-wing another form of aileron that may be employed; and

Fig. 18 is a fragmentary plan View of the aileron shown in Fig. 1'1.

The particular aileron construction shown in the drawings offers superior flight-control effects in comparison with other ailerons and can be incorporated in wings that cannot be equipped with conventional ailerons. Some airplane wings, for example, have adjacent or at their trailing edges swingable or extensible flaps that preclude the installation of aileron panels of the usual type. The present ailerons operate at the upper surfaces of the wings and substantially forward of the trailing edges of the wings.

As indicated in Fig. 2, the upper skin 20 of a wing generally desigated 2l is provided with a spanwise aileron slot 22 having a Yforward edge 23 and a rearward edge 25. Preferably the lower skin 26 of the wing has one or more openings 21 into which air may fiow as indicated by the arrows whenever the aileron slot 22 is open. n It is contemplatedY that an aileron will be provided which in retractedl disposition will substantially conform to the normal airfoil configuration of the wing 2| and at its effective or extended -position will extend above the upper skin 20 of the wing, the aileron at its retracted disposition closing the aileron slot 22. It is apparent that variousy types and constructions of ailerons may be employed to function in substantially the manner described. v Y

Lateral or rolling control of the aircraft by Vsuch an aileron arrangement is achieved both by spoiling lift in one wing and by additionally setting up positive downward reaction of the wing to the air stream. At high speedY of flight the aileron is usually only slightly lifted for a control effectand functions primarily as a deflection obstacle in the air'stream, the resultant eddies spoiling lift to a material degree yand causing drag while simultaneously the reaction of the obstacle in deflecting the air stream results in a downward thrust on the wing. Both of these two effects cause a rolling moment and both create a favorable yaw. At lower speeds of ight the aileron is extended `farther above the upper skin of the wing, but the most important factor in flight control at low speed may be the ow. of air to the upper surface of the wing through the aileron slot 22.

The specific aileron 3B in Fig. 2, which is shown to be of arcuate cross-sectional configuration, is normally telescoped into the conguration of the wing 2| and is adapted to retractably extend upward from the wing through the aileron slot 22. Since the aileron slot 22 extends across the upper edges of various ribs 3l in the wing 2l (Fig. l) the aileron 3D may comprise a number of sections'or panels 32 dimensioned to fit into the wing compartments that are separated Iby the ribs. While the individual panels -32 are shown as structurally independent of the others in Fig. l, it is apparent that they may be interconnected at their upper edges without interfering wtih the ribs 3 I.

As shown in the drawings, each of the panels 32 of the aileron 30 has a front skin 33, a corrugated reinfocement 35, channel-shapedrside walls 36, and a trailing plate or deflection 31 at its upper edge. No rear skin on the opposite side of the reinforcement 36 is necessary. The trailing plates 31 are dimensioned to cover the aileron slot 22 when the aileron is completely retracted and at such time may overlie an offset lip 38 formed in the upper skin 20 of the wing. If the sections or panels 32 of the aileron are tor be structurally interconnected, such interconnection may be provided by employing a single trailing plate 31 common to the various panels 32,

as shown in Fig. 9. In addition to functioning as an effective part of the aileron in flight control, the trailing plate 31 has the function of serving as a deflection member, the railing plate reacting to the air stream by creating a desirable tendency on the part of the aileron to retract to its normal disposition.

The aileron panels 32 may be mounted in the wing 2l for extension and retraction in any suitable manner and may be arranged to move along arcuate paths concentric to the centers or axes of curvature of the aileron panels. In the particular construction shown inFigs. 2, 3, and 4, eachY aileron panelY 32 has an arcuate track 4| mounted on each of its side walls 36, the arcuate track having a longitudinal channel 42 conforming to and engaged by suitable rollers 43. For each arcuate track lll there are two of the rollers 4&3 mounted at spaced points on one of the ribs 3|. The two rollers 43 have fixed axes of rotation but nevertheless guide the track 4l on a curved path through the aileron sloty 22 since the track itself is curved. As best shown in Figs.

3 and 4, the two rollers i3 on one side of a rib 3l may be paired with the two rollers on the other side of the rib. The two paired rollers 43 are mounted on opposite ends of a pin 45and the pin is carried by a roller bearing 4S mounted in an aperture 41 in the rib. To provide an operative connection for the actuation of each of the aileron panels 32, the inner spanwise edge of each aileron panel may be provided with a suitable wrist pin 48 set across a recessY 50.

When the Yaileron 30 is shifted along its arcuate path through the aileron slot 22 into the air stream above the wing, it becomes an obstacle against which the air stream impinges with resultant pressure against the front skin 33 of the aileron. VIt has been ascertained empirically that such pressure on the front skin of the aileron does not have any significant component tending to retract the aileron if the aileron is guided in the above-described manner along a path concentric to its own curvature of cross-sectional conguration. In other Words, if the center of i curvature of the front skin 33 of the aileron panel is at C in Fig. 2 and if the center of curvature of the aileron track 4! is likewise at C, pressure of the air stream on the aileron panel will tend neither to extend nor retract the aileron panel at any position of the panel. It will be noted, however, that with increasing extension of the aileron, the trailing plate 31 intercepts the air stream at an increasing angle and results in a correspondingly increasing tendency of the aileron to retract.

It is apparent that an arcuate aileron movable on a concentric path in comb-ination with a trailing plate o-r other equivalent deection means provides an ideal aerodynamic member for flight control in that only a minor portion of the aerodynamic forces encountered by the flight-control member are transmitted Vthrough the controlV mechanism back t'o the control stick, and yet that vf orce of minor magnitude which is perceptible to the 'pilot varies with the extension `of the control member. Such an 'arrangement gives the pilot a feel of the control mechanism that is neces- 4sary for skillful flying and yet imposes no physical burden on the pilotreven when large control areas are involved and flight is made at exceedingly high speed.

In the construction shown in the drawings, operative connection to each of the aileronpanels 32 is provided by a connecting rod 5| that is preferably adjustable in effective length. Each of the connecting rods 5| may have an end portion '52 threaded into 'an eye member 53,'the 'eye member embracing the previously-mentioned wrist pin 48. A lock nut 55 normally prevents relative rotation between the end portion 52 and the eye member 53.

The connecting rods 5| associated with the outer two aileron panels 32 are actuated vby two corresponding bell-cranks 56, while the connecting rod 5| associated with the third or innermost aileron panel is operated by a three-arm crank 51, and the three cranks comprising the bellcranks and the three-arm crank are operatively interconnected by two operating rods 53. Preferably the operating rods 58 are constructed for adjustment in effective length in the same manner as the connecting rod 5|.

'Since the particular wing 2| shown plan in Fig. l is of tapered configuration and since I prefer to 'extend the ailerons at all wing stations in like proportion to the wing chords at the stations, I may give the aileron 3Q a spanwise taper conforming to the spanwise taper of the wing. In my preferred construction, the overall configuration of the aileron 3B is that of a tapered longitudinal section of a cone. It is apparent that in the operation of such an aileron the throw of each of the connecting rods 5| must vary from the throw 'of the other two, the least throw being required for the connecting rod nearest the tip of the wing and the greatest throw being re- 'quired in the connecting rod 5l nearest the fuselage |50 of the airplane. The required differences in throw are achieved by varying the relative dimension of the arms of the two bell-cranks 56 and of the three-arm bell-crank 51.

The second and third arms of three-arm cranks 51 may be connected by two cables 6| and 62 to corresponding arms of one of two bell-cranks 53 (Fig. 5) in the fuselage 6|), the two cables being guided by various pulleys Fig. 1 shows in the fuselage GU a torque tube 55 journaled in bearings 51 and shows two control sticks 68 for optional use 'in rotating the torque tube. the torque tube 'and control sticks being of conventional construction. To complete the arrangement for controlling the ailerons 3e in the two wings of the aircraft, some means must be provided to operatively connect the torque tube 55 with the two large bell-cranks S3 in a manner to permit the required dwells in the operation of the two bell-cranks E3. The dwell in the operation of each of the bell-cranks 63 occurs whenever a control stick 6B moves past a point representing minimum retraction of the corresponding aileron 30. (Thus, a maximum swing of a control stick 68 to the left to cause maximum extension of the left aileron must include substantial movement of the control stick after the right aileron is completely retracted, and such a maximum swing to the left is possible only if there is some provision for a dwell or lost motion in the operation of the right bell-crank 63.

While various expedients may be employed to provide the required lost motion in the operation of each of the bell-cranks 63, my preferred practice is characterized by the concept of employing a rotatable member such as an armor link corresponding to each aileron 30 and arranging for movement of the control stick in lateral direction to be translated into either bodily shift or pivotal movement of the rotatable member according to whether the aileron is to operate or to dwell, the aileron being arranged to be operatively responsive only to the bodily shift of the rotatable member. Swinging of the control stick in a direction to retract one of the ailerons 3|] is translated into bodily shifting of the rotatable member until the aileron is completely retracted and thereafter continued movement of the control stick in the same direction is translated into substantially solely pivotal movement of the rotatable member. During such pivotal movement the rotatable member serves as a vpositive lock to prevent movement of the aileron.

To embody this conception I may employ a linkage such as shown in Figs. 1, 5, and 6, as will now be described.

For control of the left aileron 30, a link 1!! has a first pivot 1| at one end operatively connected to one arm of the corresponding bell-crank 63 and has a second pivot 12 at its opposite end. When it is required that the left aileron pause or dwell in the course of the operation of a control stick 68, the second pivot 12 of the link 10 is guided in a path substantially concentric to the first pivot 1|, and when it is required that the left aileron respond to movement of a control stick the second pivot 12 is guided in a path that is not concentric to the axis of the first pivot 1|, the two paths meeting at a common transition point. Thus in Fig. 5, a dotted line 13 representing the concentric path and a dotted line 15 representing the non-concentric path of the second pivot 12 meet at a transition point designated by the arrow 16 to form a single curve representing the range of movement of the second pivot point 12.

The means I prefer to employ for operating and guiding the link 1|) for the left aileron comprises the combination of a guide lever 11, a rocker member or anchoring link 18 mounted on a fixed pivot 19, and a radial arm on the torque tube 66. The guide lever 11 is fulcrumed on the radial arm 80 and has one arm 8| pivotally connected to the second pivot 12 of the link 1|), the other arm 82 being connected to the anchoring link 18.

For control of the right aileron 39, a linkage identical with that described above, but in reverse disposition, includes: a link corresponding to the link 1li, the link having a first pivot 9| and a second pivot 92; a guide lever 91 corresponding to the guide lever 11; an anchoring link 98 corresponding to the anchoring link 13 mounted on a xed pivot 99; and a radial arm |00 corresponding to the radia1 arm 8U. It is apparent that the second pivot 92 of the link 9B is guided through paths that are mirror images of the paths 13 and 15, the various paths of the second pivot 12 and the second pivot'92 forming two intersecting curves as indicated in Fig. 6.

The disposition of the various elements of the two linkages that is shown in Fig. 5 represents one possible adjustment of the control mechanism. The essence of this particular adjustment is that when a control stick 68 is in its neutral position,

a condition represented by Fig. 5,7the second pivot F2 of the link -10 is at the transition point 16 of its movement andthe second pivot 92 of the link Se is likewise at the corresponding transition point of its curve Yof movement.A When one of the control sticks 63 is swung to the left, the various parts of the two linkages take the positions shown in solid lines in Fig. 6.

The manner in which the adjustment indicated by Fig. 5 causes the control system to'function may be understood by referring to Fig. 7 in which the elevations of the'two ailerons 30 are plotted against positions of a control stick 63. yWhen the control stick is in a central neutral position relative to its range of lateral movement for rolling control of the airplane, both ailerons are at completely retracted positions. Since the second pivots of the two links 10 and 90 are respectively precisely at-the transition point of their respective ranges of movement, and since lateral shifting of the control stick causes opposite movements of the two second pivots, it is apparent that any lateral movement of the control stick from its central neutral disposition causes one aileron to be substantially locked in its dwell position and causes the other aileron to be simultaneously extended to a degree controlled by the stick movement.

While this adjustment* of the control mechanism, exempliedvby Figs. 5 and 7, may be followed in some practices of my invention, certain disadvantages may be noted. Adjustment is critical and must be made with precision. If either or both of the second pivots of the links I0 and 90 are in a dwell position, i. e. on their concentric path of movement when the control stick is at neutral disposition, there will be a central dead zone of non-responsiveness in the range of control stick movement. Even after proper adjustment is attained, such a dead zone will become apparent if any backlash or looseness develops anywhere in the control linkage. If the aircraft, furthermore, oiTers little or no response to initial movement of an aileron from its completely retracted position, such a zone will exist, i. e., if an aileron having a range of ten inches of movement has little or no control eiect in the first inch of movement from its retracted disposition, a dead zone will be apparent. Within a dead zone, the ailerons will not be sensed by the pilot through the control stick, the result of course being uneven flight control and the pilot continually sweeping the control stick from one side to the other of the dead zone.

In my preferred practice of the invention, I so adjust the operating linkage that each of the second pivots of the two links l0 and 90 is spaced from its transition point along its paths of nonconcentric movement when a control stick is atY the central neutral position. In other words, instead of placing rthe second pivot 12 of the link 10 at the transition point 16, as shown in Fig. 5, I prefer to place it at some point in the non-concentric path l5, for example, at the point indicated by the arrow |02. The second pivot 02 of the link 90 is, of course, at a corresponding position in its non-concentric path when the control stick is at neutral, the two ailerons in eect being balanced against each other through the control stick. The manner in which the control system operates under this preferred adjustment is indicated diagrammatically in Fig. 8.

The advantages to be found in this preferred arrangement are of considerable importance in practice. In the first place, the adjustment is rfirst aileron at an accelerated. rate.

"8 not critical. In the second place, the `fact that aerodynamic forces from .both ailerons are transmitted simultaneously through the linkage to the rcontrol stick in a central zone of stick movement automatically compensates for any looseness that may develop in the mechanism. In the. third place, the fact that both ailerons are normally slightly extended eliminates any sluggishness of control that might be attributable to non-responsiveness in the initial movement of anaileron from its completely retracted disposition. In the fourth place, control effects are accentuated in two small zones immediately adjacent the neutral position of the control stick, as indicated by the dotted lines |03 in Fig. 8. The dotted lines |03 represent the fact that if one aileron is extended while the other aileron is lsimultaneously retracted, the net eil'ect is the extension of the The only disadvantage in this preferred practice of my in- Vention is in whatever penalty in aerodynamic efficiency resides in having an aileron normally extended to some degree. This penalty does not, however, offset the advantages especially if it is kept in mind in designing the wing and laying out the airfoil.

One practice of my invention is characterized by the concept of having the various aileron panels in a wing respond to the control stick at different rates. For example, a relatively large plane may have three aileron panels in` each wing as indicated in Fig. 1 and the control linkage may be designed to cause the outermost :aileron panel to respond relatively rapidly to initial stick movement from neutral, the other two panels responding less quickly. v One advantage of such an arrangement in a large airplane or in an airplane having relatively extensive aileron panels is that it lightens the initial `load on the control stick attributable to the. inertia ,of`

the panels and vtherefore facilitates rapid stick movement. Another advantage is that the relatively rapid initial movement of the outermost panel makes the aircraft sensitive to the control stick to a desirable degree. In contrast,equal movement on the part of all three panels in response to initial movement of the control stick from neutral would impose a relatively large inertia load on the stick and would engender excessive control forces in response to relatively slight movement of the control stick from neutral.

The control mechanism shown in Fig. l may be changed to make this new mode ofoperation possible by changing the design of the two bellcranks 56 and changing the design of the threearm crank '51. By way of example, Fig. 10 shows such a new arrangement, the parts being shown as disposed at the neutral position of the control stick. A bell-crank |05 has been substituted Vfor the outermost bell-crank 56 of Fig. 1, a bell-crank |06 has been substituted for the bell-crank 56 associated with the intermediate panel in Fig. 1, and a three-arm crank |07 has been substituted for the three-arm crank 510i Fig'. 1. The three cranks |05, |06, and |01 are connected to the three corresponding aileron panels 32 by the previously described connecting rods 5| and are interlocked by the two previously described oper-j ating rods 58. i

The outermost bell-crank 05 has an operating arm |08 pivotally connected to the corresponding connecting rod 5| and it is important to note that the normal angle of the operating arm relative to the connecting rod 5| ,is near to or comparable to so that the initial ratiofof rotary movement of the operating arm to the transmitted longitudinal movement of the associated link 5| is nearly maximum. As the operating arm |08 rotates counter-clockwise to extend the outermost aileron, the ratio drops. The bell-crank lfor the intermediate aileron panel has a longer operating arm I| since in a tapered wing a greater range of movement is desired on the part of the intermediate panel than cn the part of theoutermost panel. It will be noted that the normal angle of the operating arm HU relative to the associated connecting rod l is substantially less than the 90 angle of maximum effect, but the normal disposition of the arm is such that the ratio of arm rotation to the ratio of transmitted longitudinal movement of the connecting rod in` creases as the control stick departs from normal position. Finally, the three-arm crank |01 has an operating arm III longer than the operating arm H0 and normally disposed at a lesser angle than the operating arm H0. Initial movement of the operating arm III causes relatively little longitudinal movement of the corresponding connecting rod 5l. but the ratio increases sharply after substantial movement of the controlstick.

The manner in which the construction of the control mechanism indicated by Fig. will cause the three panels in the wing to respond to movement of the control stick is represented by the three curves in Fig, 1l in which theelevations of the panels are plotted for various positions of the control stick. Fig. 10 clearly reects the fact that initial movement of the control stick from neutral position causes prompt and extensive movement of the outer panel but only sluggish and relatively slight movement on the partof the other two panels. As the control stick swings farther from neutral position, first the intermediate panel is accelerated, and, finally, the inner panel is accelerated. In my preferred adjustment of the control mechanism, all of the panels reach maximum elevation substantially simultaneously as the control stick reaches its limit operating position. The different heights of the curve in Fig. 11 reect the fact that in thetapered wing the panels reach various elevations at their maximum positions. While the outermost panel has the least range of extension in a wing of tapered planform, it is to be noted that by virtue of the relatively great distance of the panel from the longitudinal axis of the airplane, the panel is exceptionally effective in proportion to its area.

Aileron panels of various constructions and congurations may be employed in the different practices of my invention. I prefer, however, to employ panels of curved configuration that eX- tend and retract on curved paths because such panels have unique advantages. One important advantage is that a curved panel affords the designer control over the proportion of air pressure on the face of the panel that is transmitted to the control mechanism. Another advantage is that a curved panel may be designed to retract into a Wing space of relatively shallow depth. A further advantage is that for a given volume of available space in a wing, the panel may be relatively extensive in fore-and-aft dimension, a substantial extent of the panel remaining in the Wing for anchorage at the extreme operative position of the panel, It is to be further noted that designing a panel with a radius of curvature outside the wing makes it possible to avoid disposing the forward face of the panel at an acute angle to the upper skin of the wing when the panel isv extended. An acute angle as distinguished from an obtuse angle provides a trap in which snow and ice may accumulate.

One manner in which 'the designer may control the tendency of the panel toshift in response to pressure from the air stream is exemplified by the panel arrangement in Fig. 2 as heretofore discussed. Since both the panel and the track in Fig. 2 are concentric tothe same axis of curvature, ail-pressure on the front skin of the panel creates no tendency whatsoever for the panel to shift and the designer achieves a retracting force of whatever magnitude is desired by simply adding a deflection pla-te 3'! of a required area and angular disposition. Y 4

A second method of providing a f orce tending to shift the panel is to shape the panel andthe guide track to diiierent curvatures, lin other words, a force component tending to vshift the panel may be engendered by making the panel curvature eccentric to the` curvature of the associated track. If the curvature of the panel is modified to place its axis of curvature rearward or toward the trailing edge of the wing from the axis of curvature of the track, pressure of the air stream on the exposed face of the panel will tend to retract the panel; conversely, if the axis of curvature of the panel is shifted lto a position forward o1" the axis of curvature of the track, pressure of the air stream on the exposed face of the panel'will tendto extend the panel.

Figs. l2 and 13 illustrate a panel arrangement in which the tendency of the` panel is to retract in response to air pressure on the exposed face of the panel. Each of the aileron panels generally designated H2 has a front skin Ii, a corrugated reinforcement H5, and a pair of side plates lit. The side plates H6 are attached to curved tracks l il of the character heretofore described, each of the tracks engaging spaced rollers H8 mounted on a Wing rib 120. The axis of curvature of the panel face is located, for example, at the point P which is substantially rearward ofthe axis of curvature T of the track, Increasing the rearward spacing of the axis P relativeV to the axis T increases the tendency of the extended panel to retract in response to air pressure from the air stream.

It has been definitely established by wind tunnel tests that if an aileron of the type shown in Figs. 2 and l2 or an aileron of any conventional type is mounted for operation at the upper surface of a wing forward of the point on the wing chord, Athere will be a lag in the response of the aircraft to elevation of an aileron. The lag increases with any change in the position of the aileron forward from the ,80% point. Even a. very slight lag in response is intolerable for adequate fiight control especially in military aircraft. I have discovered that the lag in response is caused by a vacuum effect engendered rearward of the aileron when the aileron is extended above the upper skin of the wing, and I have further discovered that the lag may be eliminated by providing for passage of air directly through the aileron. Various perforated, apertured, or slotted panels may be employed when it is desirable to place the aileron forward of the 80% point, My preferred aileron for a forward position comprises a plurality of spaced spanwise vanes Which may or may not be arranged in curved alignment.

Figs. 14, l5, and 16 indicate by way of illustration the construction of a panel generally designated |2l that may be employed lat any point on 11` the upper surface of a wing forward of the Y80% point." The panel |2| comprises a plurality of spaced spanwise vanes |22 mounted in a frame that includes a pair of channel-shaped side members |23, the side members preferably but not necessarily being of curved configuration. Each of the curved side `members |23 may be attached toa curved track |25 to permit the panel to be extended and retracted in the manner heretofore described. The plurality of spaced vanes |22 not only define ample slots for air iiow through the aileron but also provide numerous deflection surfaces to the air stream. These deflection surfaces engender the required night-control forces for rolling the plane about its longitudinal axis and also provide a desired tendency for the aileron to retract into the Wing.

Y Figs. 17 and 18 show an aileron lpanel generally designated |21 constructed for operation near the leading -edge of the wing. The aileron |21 comprises a plurality of spaced spanwise vanes |28 mounted on a frame that includes a pair of triangular side plates |30, the side plates being mounted on pivots |3I. Pivotal movement of the aileron |21 in response to the aileron control mechanism shifts the plurality of vanes |28 upward to the exterior of the wing as required forv 1. In an aircraft control system the combination of two opposite aerodynamic members; a common manual control member; and a linkage operatively connecting said control member to one of said aerodynamic members to provide a` dwell in the movement of said one of the aerodynamic members while the 'other of the aerodynamic members/is being moved by the control member, said linkage including a link havingV al first pivot and a second pivot, said first pivot being operatively connected to said aerodynamic member to operate the aerodynamic member when the first pivot is shifted laterally, a lever,`

said lever having a first arm and a second arm, said first arm'being operatively connected with said second pivot ofsaid link, means operatively interconnecting said manual control member and the second arm'of said leverrto cause said lastv connection .toi shift when/the manual control memberA is moved, vand a'rocker member having a xed pivot, said lever.beingfulcrumed on said rocker member, said link, lever, and rocker member being so yconstructed and arranged that overy a portion of the range of operation of the linkage by said manual control member said second pivot of said link moves in a path substantially concentric to the axis of said first pivot of Ythe link, and over the rest of the range of operation of the linkage said second pivot of said link moves in a path non-concentric to the axis of said first pivot of the link.

said means operatively interconnecting said manual control member and thesecond arm of Vsaid lever includes a rocker arm on which said lever is mounted.

3. In an aircraft control system the combination of two opposite aerodynamic members; a common lmanual control member; and two linkages operatively connecting said control member to said aerodynamic members to provide a dwell in the movement of each' of the aerodynamic members.V while the control member is being moved, each of said linkages including a link having a rst pivot and a second pivot, said first pivot being operatively connected toi the corresponding aerodynamic member to operate the correspondingfaerodynamic member when the first pivot is shifted, a lever, said lever having a first arm and a second arm, said first arm being operatively connected with said second pivot of said link,

means operatively interconnecting said manual control member and the second arm of said lever to cause said last connection to shift when the manual control member is moved, and a rocker member having a fixed pivot, said lever being fulcrumed on said rocker member, said lever, link, and rockenmember being so constructed and arranged that over a portion of the range of operation of the linkage `by said manual control member said second pivot of said link moves in a path substantially concentric to the axis of said first pivot of the link to cause the corresponding aerodynamic member to dwell at one of its limit positions, said link, lever, and rocker'member being so disposed that the corresponding aerodynamic member is at an intermediate position in its range Yof effective positions when said manual control member is at its neutralcontrol position. l AEDWARD F. ZAP.

2. A linkage as set forth in claim I in which- Y 

